1. Field of the Invention
The present invention relates to a heating apparatus, to which an operating command can be given by voices instead of by pushing many switch buttons by hand.
2. Prior Art
In recent years, studies have been made to introduce a control system that can be actuated by voices, letters or words, signs or pictures as an aid or guide for inputting command into an electronics system, in order to attain easier and more natural communication between a user and a system. Especially, the use of a voice as an information transforming medium is attracting much attention as the most natural communication mode between man and machine. The use of voice in controlling an apparatus becomes more and more realizable, as the semiconductor technology advances by providing rapid increases of memory capacity through higher and higher circuit integrations in memory devices, and by an appearance and development of a microcomputers to be used as a controlling devices, etc.
However, the present state of the art in voice recognition techniques can not assure a perfect command recognition, i.e. there still remains a possibility that the user's voice is erroneously recognized. When a voice recognition system of an apparatus will be improved with more sophisticated hard ware in order to avoid erroneous recognition, the size of a control system incorporated into the apparatus becomes larger. This size increase hampers the introduction of a voice recognition system into household electric appliances such as a heating microwave oven type apparatus.
If a voice recognition system is installed in a heating apparatus such as an electric oven or a microwave oven, the most dangerous maloperation is an abnormal starting operation i.e. a heating operation is erroneously started without a heating command. In this case, an enclosure case and/or a door of the heating apparatus is unnecessarily heated and can sometimes be over-heated to a high temperature, thereby exposing the user to a risk of burning of the user's hands. In worst cases, the enclosure case may catch fire, or curtains or others nearby the heating apparatus may be burned by a spreading fire. In the case of microwave ovens, if such an erroneous heating operation be carried out without a heating load therein, then a leak amount of microwave radiation energy through the door might increase and besides elements such as a magnetron might be damaged thereby drastically shortening their life times. Therefore, a control system for the heating apparatus should be designed by giving careful consideration to prevent the abovementioned starting maloperation.
Another maloperation which is dangerous is the occurance of a stop command that is not acknowledged and acted upon by the control system of the heating apparatus and hence the heating operation can not be interrupted at a desired time in the middle of a heating cycle. In the following two situations the user may wish to interrupt the heating operation halfway before it is completed. A first situation is that the user wishes to confirm that how much a foodstuff is being heated, by opening the door in the middle of the heating cycle and testing its temperature. In case the user opens the door when electric power supply to the heating means still continues, he is placed in a dangerous situation. By having to reset a timer every time the door is opened for the sake of safety is troublesome, since a renewed setting is necessary for resuming the heating operation after the door has been opened. In these respects, it is preferable to provide in the heating apparatus an interruption control circuit which interrupts the heating operation for a moment.
A second situation occurs when the user wishes to interrupt the heating either because the foodstuff being heated accidentally catches fire in the heating chamber or because the heating operation was erroneously started without a normal command. Even if the heating apparatus is provided with a door switch which switches off the heating circuit once a door handle is pulled, like the case of conventional microwave ovens, it is still dangerous to open the door in order to stop the electric power supply, once the heating object catches fire inside the heating chamber. This is because oxygen is supplied to the burning object by the opening of the door thereby spreading the fire violently. Therefore, it is preferable to provide in the heating apparatus a stop control circuit which can instantly interrupt the heating operation by stopping electric power supply to the heating means with the door closed. But, even if such a stop control circuit is installed in the heating apparatus, still there may be a possibility that a stop command can not be acknowledged instantly by the stop control circuit and that the heating operation proceeds. This is undesirable and sometimes dangerous for the users. In particular, it is extremely dangerous when the user is upset or at a loss what to do, and he or she can not take necessary steps, such as, for example, pulling out the electrical power plug from the its wall socket.
Therefore, in designing a control system for the heating apparatus, it is essential to pay attention how to prevent the abnormal starting of maloperation and how to overcome the difficulties associated with inputting a command for instant stopping of the heating operation.